I concur with Joe, there never was a series I. The mds800 was the first development system (not counting the Intellec 8). What Siemens did though was contract with Intel to produce a "Siemens" development system which was of course just a different color Series II machine. They were off white and carried the Siemens logo. -----Original Message----- From: "Joe R." <rigdonj(a)cfl.rr.com> AFIK all of the MDS2xxs (including the blue ones) are series II machines. I've never heard of anything that Intel designated as a Series I. Most of the Series II machines have blue cases but some of them have white cases. The white ones are thought to be later machines but no one knows for sure. Just to further confuse the issue, ANY of the MDS2xxs can be upgraded to series III by adding a 8086 Resident Processor Card. I believe the MDS800s can also be upgraded to Series III the same way. Joe